SiC, which is superior to Si or the like in, for example, heat resistance and electrical characteristics, has attracted attention as a new semiconductor material.
Patent Document 1 discloses a surface treatment method for planarizing a surface of such SiC substrate. In the surface treatment method, the SiC substrate is heated while stored in a storing container having Si vapor pressure in its inside. Accordingly, the SiC substrate arranged within the storing container is etched, which can obtain a SiC substrate that is planar at a molecular level.
Here, the SiC substrate can be obtained by cutting out of an ingot made of single crystal SiC at a predetermined angle. When a semiconductor element is manufactured from the SiC substrate that is cut out, an epitaxial growth is performed. However, since a surface roughness is large in a state of the SiC substrate that is cut out, it is required to planarize the surface by performing steps of treatment such as mechanical polishing (MP) and chemical mechanical polishing (CMP), etc. However, polishing scratches are generated on the surface of the SiC substrate by performing mechanical polishing and chemical mechanical polishing, etc. A modified layer having disordered crystallinity that is formed by applying the pressure on the surface of the SiC substrate during mechanical polishing and chemical mechanical polishing (hereinafter, referred to as latent scratches) is generated.